Propelling device for aircraft and the like



Sept. 1, 1931, w. STELZER 1,321,450

PROPELLING DEVICE FOR AIRCRAFT AND THE LIKE Filed Sept. -7. 1928 3 Sheets-Sheet '1 h a (a Sept. i, 1931.

w. STELZER PROPELLING DEVICE FOR AIRCRAFT AND THE LEKE Filed Sept. '7. 1928- 5 Sheets-Sheet 2 NM g H I! H .ww an mm .1. NM: m a 5 km @N w v Q i. M l mm w \w mg Sept. 1, m1. w; STELZER 1,821,450

PROPELLING DEVICE FOR AIRCRAFT AND HE LIKE Filed Sept. 7, 1928 3 Sheets-Sheet 3 Patented Sept. 1.19311 UNITED S ATES P T-Eur OFFICE WILLIAM STELZER, OF CHICAGO, ILLINOIS, v ASSIGNOR TO .AIIERICAN PROPELLER COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND PROPELLING DEVICE r01? Application filed September The invention relates to an aircraft pro pulsion system comprising a main propeller and a'coaxially arrangedcounter propeller revolving in opposite direction to that of the main propeller, and a planetary speed reducing gearing, the frame carrying the axes of the planetary gears being connected to the main propeller, and the gear on whose periphery the said planetary gears travel being revoluble and connected to the counter propeller.

The object of the invention is to provide an efiicient speed. reducing gearing capable of transmitting one. and a half times as much power as a standard speed reducing gearing where the gear on whose periphery the planetary gearstravel, is stationary.-

Another object is to provide a counter pro peller revolving in opposite direction to that of the main propeller in order to enable the use of the novel reducing gearing-and to increase the propeller efilciency by preventing loss of energy due to race rotation of the air stream.

It is. well known that in order to produce thrust, air must be accelerated backwardly,

. and since the kinetic energy imparted to the air increases with the square of the .speed imparted to the air, it is apparently cheaper to increase the mass than the speed. This consideration justifies the employment of large propellers revolving at reduced speed, necessitating the use of a reduction gearing. However, the advantage gained thereby should not be bought at the price of danger. It is therefore an object of the invention to provide a safe and dependable, yet inexpensive gearing. This object is attained by the simplicity and efiiciency of thedevice, which lends itself to smooth action and-flexibility of operation.

. Fixed counter propellers are employed for ship propulsion .to prevent loss of energy due to tangential ,motion of the water caused by the innerportions of the propeller blades. I aim to incorporate the action of such counter propellers ina propeller revolving in opposite direction to that of revolutiOnofthe main propeller. Loss of energy due to tangential motion of the air in Alaonnr'r AND THE LIKE 7, 1928. Serial No. 304,477.

the slip stream ranges from one per cent in i a fast rotating propeller to twelve per cent of the power input in a propeller revolving at slow speed, such as in the case of the employment of a reduction gearing. As nonrotating counter propellers cause considerable drag and additional weight, I incorporated the desired action in a revolving propeller which at the same"time serves to produce thrust, and therefore it is free of the drawbacks of non-rota'ting counter propellers. The application of a rotatin counterpropeller permits the increase 0 the pitch of the inner portions of the propeller blades so that they may be used to generate thrust. Numerous experiments with ordinary ropellers have shown t at the increase in pitch towards the axis does not afford any increase of the efiiciency worth mentioning. Only when such a propeller is in cooperation with a counter propeller does the emplo ent of a pitch radially increasing towar s the axis become reasonable and its advantage become apparent.

I have found that if the counter propeller.

is forward of the mainpropeller a largerter is free of any race rotation, and high.

efiiciency is attained.

Another feature owing to the counter propeller is the opposition of its torque to that of the main propeller.

The invention also aims at a repulsion systemcausing ultimate conformity of the air flow in the slip streannjand since it is known that the rotation oftheair about the propeller blades decreases inversely withtha of revolution of one propeller to that of the other may be attained.

Uther objects may appear by inspection of the drawings, wherein:

Fig. 1 is a sectional view of the reducing gearing and the propellers, with the blades broken off in order not to encumber the drawings,

Fig. 2 is a sectional view illustrating a modified form of the invention, and

Fig. 3 illustrates how one embodiment of the invention, as shown in Fig. 2, may be applied to a seaplane, the counter propeller being shown of smaller diameter than that of the main propeller to illustrate how such an arrangement affords anincrease of the quantity of air passing through the propel ler disk area'dueto the contraction of the slip stream.

' The terms employed herein are used inv the generic and descriptive sense and therefore are not intended primarily as terms of limitation.

The direction of traction of the device is indicated by an arrow 1. 2 denotes the main propeller, which is axially alined with the counter propeller 3. This counter pro.- peller 3 is preferably of smaller diameter than that of the first mentioned, as the torque is only half that of the main propel.- ler, and also'tolntilize the contraction of the slip stream to increase the quantity of air passing through the propeller disk area, an

illustration of the air flow beinggiven in Fig. 3 by the lines 37.

Referring to Fig. 1, the embodiment shown is adapted to tractor airplanes, heli copters, and other craft where the propellers are forward of the power plant. The casing 4 and its cover 5 are bolted together and constitute the usual housing for the gearing. This casingd may contain oil so that the gears are continuously bathed therein. This housing may be adapted to be secured to the fuselage or to .thecrankcase of the engine, or it may be embodied therein. i

The power or engine shaft 6 is supported in the housing by the usual anti-friction hearing 7 and carries a drive gear 8 engagmg a plurality of intermediate bevel gears learned 9 journaled on stud shafts 10 mounted integra-l with the drive shaft 6 and carried by the yoke 11 whose elongated hollow hub 12 carries the main propeller which is keyed to it. vThis hub 12 is revolubly supported in the housing by the ball bearing 13 and the hub bearing 14, which, together with the anti-thrust bearing 15 guards against longitudinal displacement of the hub 12.

The intermediate gears 9 engage the bevel gears 16 keyed to the shaft 17 which is revolubly supported in the hollow hub 12 by the hub bearings 18 andv 19 and carries the counter propeller 3. .The drive gear 8 and the driven gear 16 are preferably of equal diameter and rotate about the same axis but in opposite directions. As this gear 16 is revoluble the speed reducing gearing operates as a differential mechanism, so that the propellers are self-adjusting in their speed of revolution. It is quite apparent that this construction readily lends itself to flow.

The modification illustrated in Fig. 2 entails a planetary gear drive permitting a reater'ratio of reduction of the speed of revolution than the form shown in Fig. 1,

adaptability to operation in a disturbed air plate 26 formed on the shaft 27 which is.

axially alined with the power shaft 6 and carries the main propeller 2. The shaft 27 is revolubly supported by a stand or joist. 28 secured to the frame structure of the airplane, and by a cylindrical extension 29 of the cap 30. The cylindrical extension 29 is adapted to turn in the bore 31 in the head of the shaft 27. Said extension 29 serves as a bearing for the shaft 27, the friction being very small, 'as the drive shaft 6 and the shaft 27 revolve in the same directions.

The planetary gears 24 mesh with theprevented by the annuli of the bearing 34- and the thrust bearing 35, the thrust impressed thereon by the counter propeller 3 being communicated to the principal thrust derstood y inspection of the drawings,

which illustrates the advantage gained by making'the forward propeller of smaller diameter than that of the rear one, whereby the forward propeller 3 eflects a contraction of the slip. streamthe stream lines being illustrated by 37-and a resulting increase in the quantity of air passing through the propeller disk area of the main propeller, tlereoy improving the efficiency considera ly.

While there are herein shown and described the'preferred embodiments of the invention, it shall nevertheless be understood that the invention can be carried out in ways different from that shown without departin from-the spirit and scope of the invention. Thus, for instance, in reference to Fig. 1, each intermediate gear 9 may consist of a larger and a smaller bevel gear revolving in unison about the stud 10, the larger gear being engagedby the drive gear and the smaller one engaging the driven gear. In such an embodiment the torque of the counter propeller 'may be equal to that of the main propeller. However, the

embodiments illustrated in the drawings are preferred, as they are of simpler construction and lighter weight, and the inequality of the effects of the propellers is rather an advantage than a drawback, as it permits the employment of a small counter propeller accompanied by the increase in efficiency mentioned hereinbefore.

Further embodiments, modifications, and variations may be resorted to within the spirit and scope of the invention without departing from its principle.

Therefore, I do not desire to be limited in the application of my invention nor in the appended claims to the particular embodiment, pointed out in the aflixed drawmgs.

I claim:

1. In combination, a drive gear, a driven gear coaxial with said drive gear, intermediate revoluble gears at right angles to said drive gear meshing with said drive gear and with said driven gear'to transmitpower from said drive gear to said driven gear, means for revolublysupporting ,said intermediate gears, said means for revolubly supporting said intermediate gears being revoluble about the axis of said drive gear, a counter-propeller, means for. connecting said counte'r;propeller with said driven gear to turn therewith, a principal propeller, and means for connecting said principal propeller with said means for revolubly supporting said intermediate gears to turn therewith, substantially as described.

2. A device such 1 where the propeller connected to the said driven gear has a substantially. smaller diameter than that of the propeller connected to the means for revolubly'supporting said intermediate gears, substantially as described.

3. A device such as claimed in claim 1 as claimed in claim where the smaller propeller is forward of the larger propeller, substantially as described.

1. In combination, ,a plurality of axially aligned propellers, speed reduction means for driving said propellers at different speeds, one of said propellers being of less length than another of said propellers and arranged forwardly thereof.

. 5. In combination, a pair of axially aligned propellers, common means for driving said propellers at different speeds in opposite directions, one of said propellers being .of less radial extent than the other and arranged forwardly thereof.

6. In combination, a pair of axially aligned. propellers, common means for driving said propellers at difl'erent speeds, in opposite directions, said means including combined speed reductlon and difierential mechgreater length.

' STELZER, 

